Power sweeper broom assembly and weight compensating means therefor



May 5, 1953 c. w. MOTT 2,637,055

POWER SWEEPER BROOM ASSEMBLY AND WEIGHT COMPENSATING MEANS THEREFOR Filed May 3, 1946 5 Sheets-Sheet l nrer: Tar CARL W M077 M HZiEE.

May 5, 1953 c, w, MOTT 2,637,055

POWER SWEEPER BROOM ASSEMBLY AND WEIGHT COMPENSATING MEANS THEREFOR Filed May 3, 1946 5 Sheets-Sheet 2 Q 3 R g Irv E177 5 1- CARL W MOTT May 5, 1953 c. w. MOTT 2,

POWER SWEEPER BROOM ASSEMBLY AND WEIGHT COMPENSATING MEANS THEREFOR Filed May 3, 1946 5 Sheets-Sheet 3 I 11m 20 l l //Z Ill 0 I, 7; 4,0

94 J'HI/EIYZUF CARL W MoTT W WZ E;

5 Sheets-Sheet 4 [777:7722777 CARL W Morr C. W. MOTT POWER SWEEPER BROOM ASSEMBLY'AND WEIGHT COMPENSATING MEANS THEREFOR .57 M/fMW 5.

5min

Filed May 3, 194

y 5, 1953 c. w. MOTT 2,637,055

POWER SWEEPER BROOM ASSEMBLY AND WEIGHT COMPENSATING MEANS THEREFOR Filed May 3, 1946 5 Sheets-Sheet 5 firs.-

Patented May 5, 1953 UNITED POWER SWEEPER BROOM ASSEMBLY AND WEIGHT COMPENSATING MEANS THERE- FOR Carl W. Mott, La Grange Park, 111., assignor to Elgin Sweeper Compa tion of Illinois ny, Elgin, 111., a corpora- Application May 3, 1946, Serial No. 667,070

9 Claims.

The present invention relates generally to improvements in street sweeping machines and more especially concerns a novel main sweeper broom assembly and control means therefor.

Among the objects of the invention is the provision of improved means in a power sweeper broom assembly or unit for relieving the bristles of the main rotary sweeper broom from excessive wear due to the weight of the broom structure.

Another object of the invention is to provide improved self-adjusting means for compensating for the Weight of a main power sweeper broom assembly and which acts uniformly in all operative positions of the broom, being especially adaptive to the conditions involved in the progressive lowering of the broom as the bristles wear down in the course of prolonged operation of the broom.

tegrating means for elevating and depressing the shoe structure with the sweeper broom.

According to the general features of the invention, a rotary cylindricalmain power sweeper broom is supported rotatably by pivotally mounted broom-supporting arms and is adapted .to be driven from the motive power source of the self-propelled sweeping machine, wearing down of the bristles of the broom being minimized by compensating the weight of the broom assembly by an arrangement of springs in such a manner as to relieve the bristles from the full weight thereof but yet allowing the bristles to make efficient sweeping contact with the roadway being swept.

erator and an eificient leverage and linkage system.

According to still another feature of the invention, an improved cooperative relationship is afforded of the main power sweeper broom assembly and an improved side dirt guard or shoe assembly,- the latter assembly being connected by an appropriate self-releasing linkage to be elevated from work engagement with the roadway when the broom assembly is elevated to inactive position and having independent relative movement during sweeping operation for road contour riding.

Other objects, features, and advantages of the present invention will be readily apparent from the following detailed description of a preferred embodiment of the invention taken together with the accompanying five sheets of drawings, in which:

Figure 1 is a more or less schematic side elevational view of a street sweeping machine embodying the features of the present invention;

Figure 2 is anenlarged fragmental side elevationalview of the sweeper broom assembly and cooperating dirt shoe assembly at the right side of the machine;

Figure 3 is a fragmental enlarged horizontal sectional detail view taken substantially along the line III-III of Figure 1;

Figure 4 is a more or less conventionalized fragmental vertical sectional view taken substantially along the line IVIV of Figure 2;

Another feature of the invention resides in the provision of a main cylindrical power sweeper broom assembly in which as the broom bristles gradually wear down and the broomdiameter decreases so that the broom axis drops lower, the novel compensating spring means absorbs the major proportion of the weight of the broom assembly substantially uniformly in any operative position of elevation thereof.

In accordance with another feature of the invention an improved operating device is provided for elevating the main sweeper broom to inactive Figure 5 is a fragmentary detail elevational view taken substantially in the plane of line V-V of Figure 4; v

Figure 6 is a fragmentary plan view of the cylindrical main sweeper broom taken substantially on the line VI-VI of Figure 2;

Figure 7 is a fragmentary plan view of the upper portion of one of the broom supporting arms showing details of the length adjusting structure of the arm; r

- Figure 8 is a side elevational view of that portion of the broom supporting'arm shown in Figure 7; and

Figure 9 is a fragmentary plan View, on an enlarged scale, of the dirt guard or shoe structure, taken substantially along the line IX-IX of "Figure 2.

The sweeper broom assembly of the present invention is especially adapted for use in a small size or baby street sweeping machine on the order of that disclosed in my copendingapplica- .tion for patent .Serial ,.No. 646,525,,filedFebruary p i ion, s e i ding a i yd u icgopo5 .-.9 4 6e 39W Pa n i9-;.1 i .9 i s fip i with the rear sweeping section it of the machine The sweeping section may be constructed principally or entirely from sheet metal includingside plates i9 having forwardly extendingwingportions 2i which are secured to the chassis beams 18 as best seen in Figs. 1 and 3. The chassis beams i8 may converge forwardly and support.

a steering wheel structure 21. Supporting the sweeping section it: are wheels 22 (one at each side of the machine) which may be driven in any suitable manner from the power section 15 under the control of the operator through the medium of a transmission system including a shifting lever 23 in the cab i'l. A splash guard and closure plate structure 2 3 at each side of the sweeping section 56 partially encloses the associated wheel 22 and other operating structure for the machine.

Mounted for operation partially between the forward portioncf the rear wheels 22 and accessible through appropriate cut out openings 25 in the lower portions of the side plates I9 is a main sweeper broom 2'! (Figs. 1, 2 and 6) which is of the rotary cylindrical type embodying any preferred construction and comprising radial bristles 28 mounted on a core (not shown) supported by an axial shaft 29, the bristles being confined at the ends of the broom by respective end plates 35.

Rotatably supporting the sweeper broom axle 29 is a pair of preferably identically constructed arms 3| provided with preferably separable and adjustable bearing structure 32 engaging the broom shaft. Self-adjustment of the sweeper broom 2'! to the contours of the street being swept, as well as swinging of the broom into and out of operative position is provided for by mounting the arms 3| pivotally. Since the arc of movement for the broom 2? should preferably be on as large a radius as practicable, the arms 3| are preferably of substantial length and extend obliquely upwardly and forwardly. At their forward ends, the arms 3| are provided with respective integral split bearing eyes 33 in rotatable engagement with respective stub shafts 34 and 35 (Figs. 3 and 4) at respectively the right and left sides of the operators cab 11. A retainer plate 36 is secured to the outer end of the stub 34. In the present instance, the stub shaft 34 is carried by an appropriate bracket structure 3?, and the stub shaft 35 by a bracket structure 33 respectively mounted upon the adjacent chassis frame beams !8.

For rotatably driving the sweeper broom 21, a sprocket chain 39 runs over a driven sprocket ill keyed upon the broom shaft 29 (Fig. 6) and a drive sprocket 4| carried by a stub drive shaft 32 at least in part journaled within a bore 43 in the broom arm stub shaft 34 and having a driven gear M keyed thereon and meshing with a drive pinion 45 on a drive shaft 4'1. Enclosing the gear assembly 44, 45 and the drive shaft 4'! is a housing 48 which has an inward tubular extension 49 enclosing a spline clutch assembly 50 arranged to be operated through the medium of an external handle 5! for selectively clutching and declutching the drive shaft 31 and a power shaft 52 which is appropriately driven from the power unit in the power section l5. Power for driving a side broom 53 is also transmitted through the drive shaft 4? which carries at its outer end a bevel gear 54 meshing with a suitable bevel pinion 55 on a power transmission carried within a housing 5? which supports the side broom 53 and is mounted upon the housing t8. v

jSweep-ings from the brooms 2'! and 53s are collected in a bucket structure 58 operatively disposed forwardly of the main broom 2'1.

In order to provide for slackening the drive chain 39, as when the sweeper broom 27 i to be mounted or removed, and for effecting adequate operatingltension in the drive chain, the broom supporting arms 3! are preferably constructed for adjustment as to length and for this purpose may-be made from channel stock with the respective forward end portions thereof formed as adjustable heads 59. Each of the heads 59 is formed with an offset rear end portion (it! having longitudinal adjustment slots 6! through which extend studs 62 carried by an adapter block 63 secured as by bolts 6 in the adjacent channeled end portion of the respective broom arm 31. Clamping nuts 65 threaded on the stud 52 and driving against washers El secure the offset portion 69 in longitudinally adjusted relation against the fixed adapted block 63, thereby determining the overall length of the broom arm. Any tendency of the slidable adjustment to shorten under the influence of the relative longitudinal forces created in the operation of the drive chain 39 is avoided by an adjustment or stop screw 65 threaded through a lateral car 89 on the adapter block 63 and bearing against a stop shoulder provided by a lateral integral ear 'H] on the head 59. A locking nut H carried by the adjusting screw 68 locks it in adjusted conditic-n. By preference each of the heads '59 is provided with a pair of the stop ears 70 extending in opposite directions for purposes of standardization and to enable use of a standard head at either side of the machine.

Means are provided for elevating the main sweeper broom 2'! to inactive position as desired by swinging the broom arms 3| about the pivots provided by the stub shafts 3d and 35. According to the present invention, such elevating means include a hydraulic operator i2 (Figs. 2 and 3) of the reciprocating cylinder and piston type having the cylinder thereof secured pivotally at its blind end to a supporting bracket lit carried by a cross bar (4 the ends of which are fixedly secured to stub shafts 15 which project through the side plates Hi. The cross bar and stub shaft assembly is maintained in any suitable manner in fixed, non-rotatable relation to the side plates i9. The cylinder 12 is adapted to be supplied with motivating pressure fluid from any suitable source and controlled in any appropriate manner through respective ducts T! and extends upwardly for connection of a piston rod I8 projecting therefrom by means of a knuckle 19 with a crank arm 80. By motivating the hydraulic operator [2 to retract the piston rod 18 so that the knuckle 19 assumes the lower broken line position indicated at 19 correspondingly turns a shaft 8! to which the crank 88 is fixedly secured and likewise swings respective actuating arms 82 secured fast upon the respective opposite end portions of the shaft. This action of the arms 82 operates through the medium of articulated links 83 and 84 to swing the respective broom arms 3! upwardly and thus disposes the sweeper broom 21 in its inactive position.

A clevis knuckle 85 connects each of the respective links 83 to its actuating arm 82. A

clevis 81 on the lower end of each of the links- 84 is pivotally secured as by means-of a pin 88 to a respective angular bracket 89 secured fixedly as by welding to the associated broom arm 3|. A mounting for the crank operated shaft 3! is afforded by journal flanges 90 secured to the outer faces of the. respective opposite side, plates it through which. the;sha ft projects. When. the hydraulic operator 12 releases the broom actuate ing mechanism, the broom is allowed, in so far as the hydraulic actuating system is concerned, to rest freely upon the surface to-be swept. As the bristles of the broom wear off andthebroom gradually swings down about an are as. indicated in Fig. 2, adequate slack in the actuating mechanism allows it to substantially follow the grad ually depressed positions of the broom,.the .pis ton rod knuckle gradually attaining to a position asindicated at T9". I

An integrated relationship betweeirthemainsweeperbrush assembly and'a pair of side guard or dirt shoes 9| is established through the medium .of respective links 92;connected between shoe supporting'arm 93 and the adjacent broom armi3l so that'li'ftingof the-sweeper broom will also eifect lifting of the dirt shoes. To this end, 'eachof; the-integratinglinks 82 is formed in two separable parts. including aheadedstud portion as which extendslongitudinally slidably through a laterally projecting. bracket stand swivel pad 97 carried by the bracket and is threadedly assembled with the remainder of the link, being held fixedly in longitudinally adjusted relation thereto by. means of lock .nuts 98., At its end the .link'may .be provided'witha 11 011. n as: ing a stud "Won the associated shoe-supporting arm '93.. Each .of. the arms tii'projects for wardly and upwardly, and is provided with a journal I01 pivotally engaged upon the adjacent projecting end of, the stub shaft 15 at that side of the machine. .Thus, when thebroom arms 31 are swung upwardly to lift the broom to inactive position, the links 92 will act therewith to similarly swing the dirt shoe arms 93 and thereby lift the dirt shoe members iii to inactive position. In vorder to permit a certain amount of independent relativevswinging movementpf the broom arms 3| relative to the shoe arms 93, both for accommodating such operational T6131,- tive movement as may be effected by uneven pavement contour,obstructionsand thelike over Each of thedirt shoes-9i is formed'as-a vertical :plate equipped with a tread I02 and has an in- -wardly projecting deflector member I63 disposed atan' angle todeflect dirt thrown-thereagainst by thebroom-Tl into the dirtbucketfill. A reinforcing strut plate I04 backs up the deflector.

- It is desirable that the dirt shoes-9ibe permitted to rock within limits in a verticalplane relative to the'respective supporting arms 93 andfor thisipurpose a -limited-rocking connection is afforded betweenv the supporting arms and .t-herespective shoes.

Accordingly, the shoe-engaging end 'of each respective arm- 93 is-equipped with a journal sleeve Hi5 engaged for free rocking movement with a;stub shaft;;:l-tl, secured rigidlyv to the sideof the ;,associatedshoe;.9|, as

;-by 7 means. of a, fixed base, plate I08, a. cotter .pin

I09 holding the journal against displacement from the stub shaft. A limit upon relative rocking is attained by the engagement of a laterally protruding rigid stud lid on the arm 93 engaging within a limit socket l l l of predetermined greater diameter provided therefor fixedly on the base plate 1%. Thus, the. shoe may rockabout the a-Xiscf the stub shaft Ifll within the limits defined by engagement of the stud llil within the socket lll.

Since the main sweeper broom 21 and the various structuresrela-ted thereto, and more especially-thebroom arms 3| are of necessity of fairlyrugged construction and therefore of some weight, this full unrestrained weight imposed uponthe relatively small active periphery of the broom in operation tends to cause excessively rapid wearing down of.,the bristles. According t0 the .present invention, however, a highly advantageous weightreducing-or compensating de-; vice is employed which does not entirelycounter balance the weight of the broom assembly but allows; the broom sufficient sweeping; traction while substantially relieving the bristles at the active area of the broom periphery 'ofjthe unduly wearing weight. Accordingly, each of the broomsupporting arms 3| has connected thereto yieldable compensating means eomprising an elon gated, extensible coiledspring] lj2 {Elga 3 @1 1 5) which is preferablyv so mounted as to be self adjustable to maintain fairly uniform operative compensating tension as the broom arms 3] swing to various positions with the broom. For this purpose,the compensating spring llzfor ea of th broom ar isfip me dea n 2 to the broom arm 3i throughihemedium of a stud bolt H3 secured to the spring end-and n eas w h any S ect d 9 f. a fiimm transverse series of apertures H4 in a connect ing bracket H5 fixedly secured atan intermediate point tothe outer side of the associated arm at preferably about the longitudinal center of the arm. The center of pull of the compensat: ing spring can therefore be determined by se lection of the bracket aperture l H for optimum resultsgwith anygiven assembly, and in'particu} lar with respect to the length or particulartenf sion of any spring which. may vary somewhat in any pair of. springs. 'Ijhus the adjustmentiiidi? cated ,is advantageous to secure a ipropenbahance between. the .pair of compensating springs ll2 in the machine. I l I Each of the compensating springs H2 "prefer ably extends upwardly in somewhat divergent relationto the associated broom arm 3]. ,so'la' s to impose an; oblique compensating thrust and is connected to the rear end of a. self-adjusting, tensioning link or arm I ll, the oppositeofrifb'r. ward endof which pivot'al ly secured to'irians which support it in relatively free rocking relation to adjacentstructureto permit a fullra'nge of rocking adjustment. QAt t he right side "of, the machine, this means-may comprise an upstanding ear H8 formed with ,anlintegr'al bracket structure I I9 secured-to thehQl Sling', 48 and with the adjusting arm l;llfreelyovflying th'ehous ing. At the. left side oi -the machine (Figs, .3 and 4;) an upstanding arm I20 afiords a pivotal support for the rocking arm-;;l; ll-atthatsideion a common axis-with the supportafforded by the ear I I8 at the opposite side-pf the machine. As

a matter'of convenience, the supporting arm [20 may be formed with an integral mounting sleeve I2 I which is received upon an outwardly project- .ing reduced diameter section ltjgof the stuh tii to'which the sleeve I2! is keyed in proper position and upon which it is retained by means of a retainer plate I23 secured as by means of screws I24 on the end of the stub extension. It may be noted that the pivotal mounting axis of the compensating spring arms i I1 is disposed above and forwardly of the pivotal axis of the broom arms 3|, thus aifording a highly efficient compensating action in the spring arms.

As best shown in Fig. 2, as the broom arms 3| swing up or down, appropriate corresponding swing of the self-adjustable rocking arms H1, as induced by the tension of the associated coma pensating spring I I2, assures that the spring tension will remain reasonably uniform, particularly in the various operative or sweeping positions attained by the broom 21.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention, and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

l. In combination in a street sweeping ma chine, a support structure, a main broom, an oblique arm carrying said broom at one end, a pivot connecting the other end of said arm to said support structure to allow raising and lowering of said arm and broom, said arm being longitudinally adjustable, means for maintaining the longitudinal adjustment of said arm in opposition to a generally longitudinal thrust on said arm tending to shorten said arm, and a counterbalancing tensioned spring connected to a medial point on said arm and secured to said support structure immediately above and beyond said pivot to have a length in the raised position of said arm greater than the length of said arm from said medial point to said pivot and to define a small acute angle between the arm and the counterbalancing tension spring and to apply substantially the same torque on said arm for counterbalancing the weight of said broom in both its raised inactive position and its lowered brushing position.

2. In combination in a street sweeping machine, a support structure, a main broom, an arm carrying said broom at one end, a pivot connecting the other end of said arm to said support structure to allow raising and lowering of said arm and broom, means secured to said arm and to said support structure for raising said broom through a narrow angle, and a counterbalancing tensioned spring independent of said raising means and connected to a point on said arm and secured to said support structure immediately above and beyond said pivot to have a length in the raised position of said arm greater than the length of said arm from said point to said pivot, said counterbalancing spring applying substantially uniform torque to said arm and said broom in any position thereof to relieve the bristles of the broom of the weight of the broom and the arm in any lowered active position of the broom and to relieve the raising means of the weight of the broom and arm in the raised inactive position of the broom.

3. In combination in a street sweeping machine, a support structure, a main broom, an oblique arm carrying said broom at one end, a pivot connecting the other end of said arm to said support structure to allow raising and lowering of said arm and broom, means secured to I said arm and to said support structure for raising said broom, said raising means including a lost motion connection to said arm to isolate said raising means from motions of said arm in its lowered position, and a counterbalancing tensioned spring independent of said raising means and connected to a medial point on said arm and secured to said support structure immediately above and beyond said pivot to have a length in the raised position of said arm greater than the length of said arm from said medial point to said pivot and to define a small acute angle between said arm and said spring, said counterbalancing spring applying substantially uniform torque to said arm and said broom in any position thereof to relieve the bristles of the broom of the weight of the broom and the arm in any lowered position of the broom and to relieve the raising means of the weight of the broom and arm in the raised inactive position of the broom.

4. In combination in a street sweeping machine, a support structure, a main broom, an oblique arm carrying said broom at one end, a

' pivot connecting the other end of said arm to said support structure to allow raising and lowering of said arm and broom, means for raising and lowering said broom including power cylinder means secured to said support structure and an articulated member connected to said power cylinder means and to said arm and tensioned by said power cylinder means to raise said arm, said articulated member being sufficiently slack in the lowered brushing position of said broom to allow free movement to said arm, and a counterbalancing tensioned spring independent of said raising means and connected to a medial point on said arm and secured to said support structure immediately above and beyond said pivot to have a length in the raised position of said arm greater than the length of said arm from said medial point to said pivot and to define a small acute angle between said arm and said spring, said counterbalancing spring applying substantially uniform torque to said arm and said broom in any position thereof to relieve the bristles of the broom of the weight of the broom and the arm in any lowered active position of the broom and to relieve the raising means of the weight of the broom and arm in the raised inactive position of the broom.

5. In combination in a street sweeping machine, a support structure, a rotary main sweeping broom, means for rotating said broom, supporting arms pivotally mounted from said structure at one end of each thereof and supporting said broom at the other end of each, means for swingingly elevating said arms through a narrow angle to carry the broom into inactive position, dirt shoes adjacent the opposite ends of the broom, arms pivotally mounting said dirt shoes on said structure, means connecting the broom supporting arms and the shoe supporting arms for effecting elevation of the shoes by upward swinging of the shoe supporting arms when the broom supporting arms are swung up for elevating the broom, and counterbalancing tension springs independent of said means for swin ingly elevating said broom supporting arms and connected at one end of each thereof respectively to a medial point on said broom supporting arms, the other end of each of said counterbalancing tension springs respectively connected to said supporting structure immediately above and beyond the pivotal mounting for said broom supporting arms thereby defining a small acute angle between said counterbalancing tension springs and said supporting arms respectively, the counterbalancing tension springs operating upon said broom supporting arms to sup-- port the weight thereof and the broom assembly andapplying substantially uniform torque to said arms and broom assembly in all positions thereof, thereby relieving the bristles'of said broom of the weight ofthe broom assembly. when the broom is in its active position and relieving the elevating means of the weight of said supporting arms and broom assembly when placed in inactive position. l f

6. In combination in a street sweeping machine, a support structure, a rotary main sweeping broom, means for rotatingsaid broom, support arms pivotally mounted from said structure at one end of each thereof and supporting said broom at the other end of each, means for swingingly elevating said arms to carry the broom into inactive position, said means for swingingly elevating said arms including a lost motion connection to said arms to isolate said means from motions of said arms in its active position, dirt shoes adjacent the opposite ends of the broom, arms pivotally mounting said dirt shoes on said structure, means connecting the broom support arms and the shoe support arms for effecting elevation of the shoes by upward swinging of the shoe support arms when the broom support arms are swung up for elevating the broom, and counterbalancing tension springs connected at one end of each thereof respectively to medial points on said broom support arms, the other end of said counterbalancing tension springs respectively connected to said support structure immediately above and beyond the pivot mounting for said support arm thereby defining a small acute angle between said counterbalancing tension spring and said support arms respectively, the coun terbalancing tension springs operating upon said broom support arms to support their weight thereof and the weight of said broom assembly and applying substantially uniform torques to said arms and said broom assembly in all positions thereof, thereby relieving the bristles of said broom of the weight of the broom assembly when the broom is in its active position and relieving the elevating means of the weight of said broom assembly when placed in inactive positions.

7. In combination in a street sweeping machine, a support structure, a rotary main sweeping broom, means for rotating said broom, support arms pivotally mounted from said structure at one end of each thereof and supporting said broom at the other end of each, means for swingingly elevating said broom support arms to carry the broom into inactive position, an articulated member connected to said elevating means and to said arms and tensioned by said elevating means to raise said arms, said articulated memher being sufficiently flexed in the active brushing position of said broom to allow free movement of said arms, dirt shoes adjacent the op posite ends of the brooms, arms pivotally mounting said dirt shoes on said structure, means connecting the broom support arms and shoe support arms for effecting elevation of the shoes by upward swinging of the shoe support arms when the broom support armsare swung up for elevating the broom, and counterbalancing tension springs connected at one end of each thereof respectively to a medial point on said broom support arms, the other ends of said counterbal- =lieving the elevating means of the weight of said broom assembly when placed in inactive position.

8. In combination in a street sweeping machine, a support structure, a main broom, an

"oblique arm "carrying said broom at one end, a

pivot connecting the other end of said arm to said support structure to allow raising and lowering of said arm and broom, a dirt deflecting shoe, a pivoted shoe supporting arm, a pivotal connection between the shoe supporting arm and the shoe to permit relative rocking movement of the shoe for self-adjustment to the surface over which it travels and interengaging means on the shoe and the shoe supporting arm for limiting said rocking movement, means interconnecting said shoe supporting arm and the broom carrying arm to raise said shoe when said broom is raised, a counterbalancing tensioned spring connected to a medial point on said arm and secured to said support structure immediately above and beyond said pivot at said other end of said arm to have a length in the raised position of said arm greater than the length of said arm from said medial point to said pivot at said other end of said arm and to define a small acute angle between the arm and the counterbalancing tension spring and to apply substantially the same torque on said arm for counterbalancing the weight of said broom in both its raised inactive position and its lowered brushing position.

9. In combination in a street sweeping machine, a support structure, a rotary main sweeping broom, means for rotating said broom, support arms pivotally mounted from said structure at one end of each thereof and supporting said broom at the other end of each, said broom support arm being longitudinally adjustable, means for maintaining the longitudinal adjustment of said broom support arm in opposition to a generally longitudinal thrust thereon tending to shorten said broom support arms, means for swingingly elevating said broom support arms to carry the broom into inactive position, an articulated member connected to said elevating means and to said arms and tensioned by said elevating means to raise said arms, said articulated member being sufficiently flexed in the active brushing position of said broom to allow free movement of said arms, dirt shoes adjacent the opposite ends of the brooms, arms pivotally mounting said dirt shoes on said structure, a pivotal connection between the shoe support arms and the shoes to permit relative rocking movement of the shoe for self-adjustment to the surface over which it travels, interengaging means on the shoes and the shoe support arms for limiting said rocking movement, means connecting the broom support arms and shoe support arms for effecting elevation of the shoes by upward swinging of the shoe support arms when the broom support arms are swung up for elevating the broom, and counterbalancing tension springs connected at one end of each thereof respectively to a medial point on said broom support arms, the other ends of said counterbalancing tension springs respectively connected to said support structure immediately above and beyond the pivot mounting for said broom support arms thereby defining a small acute angle between said counterbalancing tension springs and said support arms respectively, the counterbalancing tension springs operating upon said support arms to support the weight thereof and said broom assembly and applying substantially uniform torques to said broom assembly in all positions thereof, thereby relieving the bristles of said broom of the weight of the broom assembly when the broom is in its active position and relieving the elevating means of the weight of said broom assembly when placed in inactive position. CARL W. MOT'I.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Haas Feb. 14, 1888 Konigstein Mar. 24,. 1903 Seymour Apr. 20, 1909 Banks Apr. 21, 1916 Maier Apr. 23, 1918 Jemmison Nov. 4, 1924 Clapp May 26, 1925 Wilson Mar. 18, 1930 Presbrey Apr. 18, 1933 Drumm Mar. 19, 1940 'Ieager Dec. 30, 1941 Wilson June 16, 1942 Milz Apr. 

